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Premium Member
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Discussion Starter #1
Hi All,
The SLC has cruise control with brake function so if I am going through the variable speed cameras say the M6 at Birmingham (that's UK!).
If I have the cruise set to 60mph and try to speed up between cameras, (tut tut), then the auto brake function applies and tries to pull me back to the set speed.

Question is when the auto cruise brakes are applied does it activate my brake lights.
Can't tell without following an SLC so this is just a bit of an anorak question?
 

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Premium Member 2007 SLK55 AMG
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3,554 Posts
I would assume so, any braking action by the car would also activate the brake lights for safety.
If it detects a car in front and thinks that you haven't taken action I assume it will, brake for you and the brake lights may even flash to warn drivers behind you.
Does the car automatically read and adjust your cruise control depending on the speed limit signs?
 

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Premium Member 2007 SLK55 AMG
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3,554 Posts
Normally you can accelerate when cruise is active and if you take you foot off the accelerator it normally jus
t slowly returns to the set speed without braking.
Do you have automatic cruise control where you can set a distance from the car in front? Adaptive Cruise Control?
 

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Premium Member
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Discussion Starter #4
No mine has no facility to set a distance but if I speed up above the setting as soon as a take my foot off the accelerator you can feel the brakes being gently applied then you can feel the brake go off once the speed drops down to the set figure.
I imagine you're right that the brake lights would need to come on for safety reasons even though the braking is quite gentle.

The car does have an emergency brake system, if a car in front suddenly slows down or brakes it will apply my brakes and beep loudly but that's a separate system.
 

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Premium Member 2007 SLK55 AMG
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Try cruising at say 70 on a clear road, no cruise control on, then lift off, does it feel the same?

I can't imagine the system would brake to maintain a set speed.

Someone with a 172 may be able to give you their input. None of my cars brake after accelerating with cruise on. My Skoda with an advanced Adaptive Cruise allows me to accelerate and then I can just let it take over again, it will only brake if it gets close to another vehicle ahead or in a lane on the right, I can override the the second one by tapping the accelerator.
 

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Super Moderator CA 2012 SLK55 AMG w/P30
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12,438 Posts
Ya, it brakes to bring you back to what you set it up. Don't know if the lights go on though. The brakes also go when going down a hill to maintain set speed but again, I don't know if the lights go on.

Some day I might find out with wifey behind me in another car.

But honesty prevails here: I don't care. I only care about the lights in front of me :tu:
 

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Premium Member
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Discussion Starter #7
yes it definitely applies the brakes to get you back to the set speed.

All my previous cars with cruise allowed you to accelerate to any speed and just let you coast back to the set speed.
This was handy for overtaking on a motorway.

Can't do that now without turning off cruise otherwise you would overtake a vehicle then brake once you got in front of it!
If the brake lights come on it could be unnerving to the vehicle just overtaken.
 

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Premium Member 2018 SLC43
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2,464 Posts
yes it definitely applies the brakes to get you back to the set speed.

All my previous cars with cruise allowed you to accelerate to any speed and just let you coast back to the set speed.
This was handy for overtaking on a motorway.

Can't do that now without turning off cruise otherwise you would overtake a vehicle then brake once you got in front of it!
If the brake lights come on it could be unnerving to the vehicle just overtaken.
Now I'm a big user of cruise control, but like any good advanced driver You cruise along at say ~65mph on the Motorway sitting on Cruise Control, then if I need to move into the 3rd lane to overtake a slower moving vehicle, I speed up to ~70mph and once passed the vehicle I then lift off the gas peddle to settle back down to the Cruise Control speed...

Though I agree with the Cruise Control holding My speed while descending a hill (Which the R171 does) applying the brakes after an over take manoeuvre is a step back wounds.... :surprise:

Can any other SLC drivers chip in here?
 

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Discussion Starter #9
Just had a shufty around other forums on this and it does seem there is split views on whether the brake lights come on or not.
Most folks are convinced the brakes are applied especially going downhill.
One person did suggest, (and I hadn't considered this), is that the auto transmission may well provide the braking effect by changing down and its gentle engine braking that's slowing me back down to the set speed and not gentle braking.
I hadn't spotted any change in the gear display but then I wasn't looking for it and of course the nine auto speed box is so smooth on its gear changes.
I'll watch out for it next time and report back, I think this makes better sense than using the brakes, although it still slows you down faster than just staying in the same gear, never had this issue with a manual box!:wink:
 

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Registered 2012 SLK55 AMG w/P30
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3,440 Posts
The short definitive answer is “yes”. Brake lights come on when cruise control braking is used.
 

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Registered 2016 SLC200
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30 Posts
I can confirm that the brake lights do come on - I experimented at night and could see the red glow from road signs. I don't have adaptive cruise control but obviously the software is common and some of the functionality is retained even when the option isn't activated.
I'm aware that it might confuse following drivers occasionally so if I've just overtaken someone and wish to slow to my original speed I just ease back on the accelerator without taking it right off, and the car slows more gradually without braking. I don't think the brakes are applied if it's only a few mph to knock off and the car is slowing anyway - clever stuff!
 

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Super Moderator CA 2012 SLK55 AMG w/P30
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12,438 Posts
@Pyecrust DId my cruise/brake light test.

Booted Lorraine out of the car at the crest of a hill turned around and then came back the same way with cruise set.

After starting downhill, I put my hand up to indicate the car was slowing (to maintain the set speed rather than speeding up because of the downhill glide). Lorraine said the lights came on and I wasn't braking.

So it's automatic. Car brakes because of cruise being on ----> Brake lights come on automatically (as others have already said) :tu:

Found a somewhat related thread (albeit for a 171) https://www.slkworld.com/slk-r171-general-discussion/426050-cruise-control-speed-lowering-how-does-work.html
 

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Super Moderator CA 2012 SLK55 AMG w/P30
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12,438 Posts
My R170 facelift cruise slows on downhills.
But I think the question was: do the brake lights come on when that happens. And they do.
 

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Premium Member
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Discussion Starter #17
@Pyecrust DId my cruise/brake light test.

Booted Lorraine out of the car at the crest of a hill turned around and then came back the same way with cruise set.

After starting downhill, I put my hand up to indicate the car was slowing (to maintain the set speed rather than speeding up because of the downhill glide). Lorraine said the lights came on and I wasn't braking.

So it's automatic. Car brakes because of cruise being on ----> Brake lights come on automatically (as others have already said) :tu:

Found a somewhat related thread (albeit for a 171) https://www.slkworld.com/slk-r171-general-discussion/426050-cruise-control-speed-lowering-how-does-work.html
Well done, the mystery has been solved!:smile:
 
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